The present invention relates, generally, to an apparatus and method for treating herniated discs. More particularly, the present invention relates to an ultrasound method and apparatus for first softening a damaged disc region before removing the portion of the disc causing pain. The removal of the softened herniated disc material is preferably done with a Nucleotome.RTM. system as described herein.
A herniated disc causes the patient pain by applying pressure against spinal nerves. For over thirty years, the surgical approach has involved open surgical procedures. However, such procedures may be accompanied by complications, such as damage to ligaments, lamina, and the vertebral joints, irritation of the dural sac or nerve roots, as well as occasional post-operative hematoma even infection and formation of the scar tissue. Microsurgical techniques have been used since around 1975. Although microsurgical techniques reduce the overall surgical trauma suffered by the patient, highly specialized instruments must be used In combination with a microscope. Thus, microsurgical techniques are much more intricate, time-consuming, and stressful than open surgical procedures.
One open nonsurgical method of treating herniated discs is shown in U.S. Pat. No. 5,458,596 to Lax et al. This method uses radio frequency or other forms of energy to shrink collagen connective tissue. However, such methods have not proven to be very effective. Moreover, this method treats the disc at the dorsal exterior of the disc outside the annulus and, therefore, increases the risk of damaging the adjacent spinal cord or spinal nerves. It is not used or reported in any substantial series of cases.
Another nonsurgical method of treating herniated discs is the use of chymopapain and chemonucleolysis. However, injection of chymopapain into the lumbar nucleus pulposus may be accompanied by such complications as hypersensitivity to the drug (i.e., allergic reactions, which may result in anaphylaxis), transverse myelitis, subsequent paraplegia, and even death. A popular current method of treating lumbar disc herniation involves the use of a discectomy system manufactured by Surgical Dynamics and sold under the trademark Nucleotome.RTM. System. This system involves insertion of a guide pin trocar into the area to be treated, and subsequent insertion of a cannula with a tapered dilator over the guide pin. A trephine is placed over the guide pin and through the cannula and rotated to create an incision through the annulus into the disc. The trephine and guide pin are then removed, leaving the cannula in place. Next, a Nucleotome.RTM. probe is inserted into the cannula. The probe suctions a portion of the disc into the probe's hollow interior, where the disc is cut and suctioned away. Complications such as clogging of the probe and removal of an inadequate amount of disc material may occur.
While the use of ultrasonically vibrated tools for aspirating various tissues is known in the art, they have not been applied to the removal of herniated disc material within the annulus fibrosis. Current discectomy methods either disintegrate portions of the disc, or suction portions of the disc, which is often difficult because of the consistency of the disc material. With currently known procedures, a Dong tube (the Nucleotome.RTM.) is inserted within the annulus into a damaged disc region and small pieces of disc material are drawn out through the tube by a stream of fluid aspirated into the region and a vacuum applied to suction material out of the region. The vacuum sucks a small amount of disc material into the tube, where it is sliced off by a cutting blade with a guillotine-like action. Water running through the tube flushes the material out. The cycle is repeated until an adequate amount of disc is removed which reduces the pressure on the spinal nerve(s) or spinal cord, or both, depending on the area being treated.
U.S. Pat. No. 3,589,363 to Banko et al. shows the use of an ultrasonically vibrated instrument for disintegrating unwanted tissue, such as a cataracted lens, in an eye. A first passage in the instrument is provided for carrying treatment fluid to the region to be treated, and a second passage is provided for carrying a suspension of unwanted material in the treatment fluid away from the treated area. Additionally, U.S. Pat. Nos. 4,016,882 and 4,136,700 to Broadwin et al. also show the use of an ultrasonically vibrated tool for disintegrating or comminuting soft tissue which is then aspirated through the hollow tip of the device. The tube is vibrated transversely with respect to the longitudinal axis of the tip and to the direction of contact. Ultrasonic vibration is accompanied by simultaneous aspiration. The disclosed device may allegedly be used to excise spinal column tumors.
Another use of an ultrasonically vibrated instrument is shown in U.S. Pat. No. 5,167,619 to Wuchinich. The Wuchinich instrument is allegedly usable to melt cement in a bone without affecting the integrity of the bone. The melted cement material is said to be drawn into the tip by applied suction. The tip may also be rotated so that the cement is exposed to shearing as well as axial vibration.